Sharp EL-5230 4.217, 7.424, Twinkle, twinkle, little star Apparent magnitude of stars, Result

Chapter 8: Application Examples

6.Press @ c 02 e 5.976 ` 24 e.

•Use the physical constants function for the G value.

TŒ=(4πŒ)©(GM)˚ R„ R=z 0.000

•After completion of entering values for variables G and M, the cursor moves on to variable R. (The variable T has already its value.)

7.Press @ h.

Result

Geosynchronous orbit is possible approxi- mately 42,170 km (4.217 ⋅ 107 meters) from the center of the Earth.

R=	4.217
R¬	7.424
L¬	7.424

Twinkle, twinkle, little star (Apparent magnitude of stars)

The apparent magnitude of a star is a measure of how bright it appears. It is a function of how far away the star is and the luminosity of the star.

Since stars are seen from different distances, their luminosities must be standardized before they can be compared. This is done using a quantity called the absolute magnitude, which is a measure of how bright that star would appear if it was viewed from a distance of 10 parsecs (about 32.6 light years).

If the absolute magnitude of two stars is known, the ratio of their luminosities is given by the equation.

L2

Log —— = 0.4 (M1 – M2)

L1

where M1 = Absolute magnitude of the first star M2 = Absolute magnitude of the second star L1 = Luminosity of the first star

L2 = Luminosity of the second star

111